Meru and Maha-Meru are different things. Maha-meru are big in size and usually established in temples or peethams. The pooja process is same of that of the sri chakra. Meru is the 3D form of normal sri yantra. The process of worship is mentioned in authentic books like "Nityotsava". However, one must be initiated in the vidya in order to do ritualistic pooja as per shastra.
Srichakra is the diagrammatic representation of Shiva-Shakti in the Cosmic and the individual aspects. In the Hindu Tantras, there are three kinds of external symbols used for worship of the Supreme Being who is Himself formless and nameless. The most external is the image cast in the human forms but with paraphernalia signifying supra-human divinity. The last and the subtlest are the Mantras, which are Divine sounds or Bijaksharas or letters indicating certain indeclinable seed sounds. A Mantra is divine power clothed in sound. Between these two come Yantras, also called Chakras, which are representations of the Deity in geometrical diagrams.
The Srichakra is conceived as Shiva-Shakti in the macrocosmic as well as in the microcosmic aspects i.e. as the cosmos and the individual. The Chakra consists of a series of nine triangles superimposed around a central point called Bindu, forming forty-three Konas or triangular projections. In the center is the Bindu, representing Shiva-Shakti in union in the causal state from which all the other parts of the diagram representing the cosmos are evolved. The Bindu is in a central triangle with apex downwards in the Samhara Chakra of the Kaulas, but in the Srishti Chakra of the samayins, it is below the base of the central triangle with its apex upwards. Enclosing it and superimposed on one another are the four Shiva triangles with apexes upward and five Shakti triangles (inclusive of the inner triangle) with apexes downward. Two circles of lotuses, one with eight petals and the other with sixteen petals surround these. Outside these, are three circles around and a rectangular enclosure (Bhupura) of three lines for the entire Chakra, with four entrances on the four sides.
The central Bindu stands for Shiva-Shakti in the causal state of creation. Shakti is here represented as Mahatripurasundari, the great Mother or the incomparable beauty of the three Puras or three Bindus. The Bindu represents the initial pushing forth of massive or ghanIbhUtA Shakti, with the potentiality of the universe within itself. It is spoken of as three to indicate the three stresses when the unified non-dual Shiva- Shakti seem to separate into two aspects Prakasha (the Aham or I consciousness) and Vimarsha (the idam or this-consciousness). These three stresses are technically called Nada, Kalaa and Bindu. Naada is the inchoate sound movement (interpreted by human ear as Omkara) and Kalaa is the Kaama Kalaa, the desire to create, which the Vedas represent as 'May I be many'. Bindu is the potential universe ready to separate into various categories. All these three stresses of Shiva-Shakti together are represented by the central red Bindu with an imaginary line across it to represent the polarity in the supreme category as Shiva-Shakti. The great Bindu, the threefold stress of the externalizing or creative Shakti is indeed the divine mother Mahatripurasundari. She is described as 'puramathiturAho puruShikA' in the seventh verse of Saundaryalahari, popularly interpreted as the 'Pride of Shiva'. It however really means that Shiva as Prakasha (Luminosity or consciousness) realizes Himself as 'I am', through Her, the Vimarsha Shakti (the Object as the reflector).
The rest of the Srichakra represents the whole of the Brahmanda (cosmos) as evolved from the Bindu, standing for Mahatripurasundari. Surrounding the Bindu is a series of overlapping triangles. These nine triangles constitute the nine basic categories of the universe, evolving from the supreme mother Mahatripurasundari represented by the central Bindu. Hence they are called Mula Prakritis or root substances of the universe. The Shiva and Shakti triangles are superimposed to indicate that Shiva and Shakti are involved in the whole process of ‘Becoming’ in its microcosmic and cosmic aspects. In the individual, they are present as the nine Dhatus or substances constituting the physical body. These are Tvak (skin), Asrk (blood), Mamsa (flesh), Medhas (fat), and Asthi (bone). These five categories are born of Shakti element while the evolutes of the Shiva elements constitute of shukla (semen), majja (marrow), prana (vital energy) and Jiva (the individual soul). On the cosmic side, the five constitutes of Shakti are the five elements (pancha mahabhutas i.e. earth, water, fire, air and space) and the five Tanmatras (subtle elements), the five karmendriyas (organs of action), the five Gnanendriyas (organs of knowledge) and Manas (mind)- these have their origin in the Shakti element, while Maya, Suddha Vidya, Maheshwara and Sadashiva form the Shiva element. Thus the nine basic triangles symbolize the twenty-five elements or Tatvas that constitute the cosmos and the individual bodies.
The poojan is done in 9 stages where each "avarana" is done with the corresponding deities. Hence the pooja is also known as "Nava-avarana pooja".
Each of the nine Aavaranas of the Srichakra has a speical significance.
Trailokyamohana Chakra: Here, the word Loka indicates Maata, Meya and Maana i.e the seer, the object seen and the act of seeing itself or in other words Kartru, karma and kriya. The compound of these three is Trailokya. This great chakra enchants these three i.e the trailokya and dissolves the three into a single non-dual entity which is what leads to complete Advaita.
Sarvaashaaparipooraka Chakra: Here, the word Asha indicates the insatiable desires of the mind and the senses which lead us more and more towards duality. This great Chakra grants all desires by uniting its Sadhaka with the ever satisfied, all fulfilling, eternal Parabrahman or Paramashiva. This stage is indeed the Kamakoti the state of accomplishment of all desires or actually going beyond all desires by achieving the most desirable thing, which indeed is the liberating Brahma Jnana.
Sarvasamkshobhana Chakra: During dissolution, all Tatvas right from Prithvi upto Shiva dissolve into one another. This great Chakra creates the destructive agitation (Kshobha) in all the Tatvas causing duality, thus dissolving any duality in the Sadhaka. It agitates and destroys duality in the sadhaka.
Sarvasoubhagyadayaka Chakra: Saubhagya is something that is desired by everyone. This great Chakra grants the most desired object to the Sadhaka which is nothing but the great Paramashiva or Mahatripurasundari. What greater fortune or Bhagya does a sadhaka long for other than his beloved mother? Thus this Chakra is indeed Chintamani - Kalpataru - Kamadhenu, all put in one.
Sarvarthasadhaka Chakra: The ultimate goal of all Vedic and Tantric rites and ceremonies is the attainment of Paramashiva. Various scriptures elaborate numerous methods to achieve this final beatitude. In the same way as all rivers merge into the great ocean finally, any of these legitimate means take the Sadhaka to the same destination. This great Chakra results in the Siddhi of all these paths or means i.e it grants the final Siddhi which is doubtlessly Parabrahma Prapti.
Sarvarakshaakara Chakra: This great Chakra protects the Sadhaka from all forms and kinds of Avidya and duality, which are the only reasons for misery and grief. The visible world, constituted of the 36 Tatvas is impermanent and since these Tatvas grant Bhedadrishti or a sense of separation between the Atman and the Paramatman, the world has to be rejected as falsehood. By flooding the Sivaaham Bhavana (the sense of Iam Shivaa i.e the Advaita Bhavana) through the Sadhaka, this Chakra protects him from the treacherous Samsara composed of 36 Tatvas, all leading to duality. When the Sadhaka realizes himself and the entire world as not separate from Paramashiva, he is automatically protected from Avidya. What this Chakra does is to destroy 'Idamtaa or sense of this' by the pure awareness of 'Ahamtaa or I-ness'.
Sarvarogahara Chakra: There is no worse disease than Samsara which induces duality. Due to its constituent 36 Tatvas which are different from each other. This great Chakra destroys the disease of this Samsara which is the root cause of all other types of diseases. When Vamakeshwara Tantra and also the Mudra kanda of Rudrayamala speak of Khechari as destroying all diseases, this is what is hinted at.
Sarvasiddhiprada Chakra: Yoginihridaya says that this Chakra indicates the potentiality to create - maintain - destroy the universe. As Pratyabhijnaahridaya says 'Chiti Shakti is indeed responsible for the Siddhi of the universe'. Thus, the trikona or the triangle Chakra is responsible for creation, destruction and preservation, while the other two acts namely Tirodhana and Anugraha are indicated by these three only.
The state of complete harmony of Shiva and Shakti exists in Sarvaanandamaya Chakra. Thus this Chakra is the very personification of eternal, limitless bliss. This grants Brahmananda to Sadhaka.
